Energinet has awarded the contract for the buildings that will house key electrical infrastructure for Bornholm Energy Island in Denmark to Per Aarsleff A/S - a Danish contracting and infrastructure group with experience in large and complex construction projects. The award marks another important step in the joint Danish-German project developed by Energinet and 50Hertz.

The contract covers buildings for three converter stations in Denmark — one on Zealand and two on Bornholm — as well as the building for a new 400 kV high-voltage station on Bornholm. It also includes site preparation, access roads and related civil works around the station areas.
Bornholm Energy Island is being developed jointly by the two transmission system operators Energinet in Denmark and 50Hertz in Germany. The project will connect offshore wind power in the Baltic Sea with the electricity grids in Denmark and Germany and support a more integrated and resilient European energy system.

With the selection of Aarsleff, the project moves further towards the construction phase. The coming period will focus on detailed design and planning before construction is expected to begin in 2027.

Once completed, the infrastructure will help collect and transmit large amounts of renewable electricity from future offshore wind farms near Bornholm to consumers in Denmark and Germany.

Visualisation: C.F. Møller Architects

Architecture and landscape integration on Bornholm: The contractor’s proposal uses materials, colours and landscaping that reference Bornholm’s geology and landscape for the projects main station on Bornholm. Concrete bases, natural stone façades and earthy tones give the buildings a calm architectural expression, while planting, terrain modelling and pathways help screen the facility and integrate it into the surrounding landscape in line with the local plan.

Buildings for the key facilities on Bornholm: The visualisation shows the largest buildings to be constructed on Bornholm: four converter halls and a GIS building. The area marked “Construction Site Facilities and Laydown for BEI” on the map is reserved for future DC breakers. They are not part of the current project, but they have been included in the planning, as they are essential for future connections.

Energinet has selected STM Entreprise, a Bornholm-based company, to handle the demolition of buildings where the future transformer station for Bornholm Energy Island will be established.

The contract was tendered from 27 March to 30 April 2026, with five companies submitting bids – two of which were local. STM Entreprise was awarded the contract, and demolition is expected to begin on 1 June 2026.

Brian Kofoed, CEO and owner of STM Entreprise, says:

“It means a lot to us as a Bornholm company to help shape the island’s future and contribute to such a major project. We look forward to starting the work and to good cooperation with Energinet and its partners.”

Kim Søgaard Mikkelsen, Project Director for Bornholm Energy Island at Energinet, is also pleased with the choice:

“We are delighted that a local contractor has been awarded the task. The project is substantial, and we strive to make a positive contribution to the area. It is also positive that the contractor is focusing on reusing materials from the demolition. This is entirely in line with our ambition to undertake projects with regard for both the environment and resources.”

The demolition marks the first step in the physical preparations for Energy Island Bornholm, which, together with the associated offshore wind farms, is expected to be operational in 2036.

Photo: STM Enterprise (Stock Photo)

After a thorough environmental assessment and several rounds of public consultation between 2022 and 2025, the Bornholm Energy Island project has received the environmental permit for the onshore and offshore facilities and cables. This sets the framework for construction, ensuring it’s carried out with the greatest possible care for people, nature, and the environment. The permit covers onshore installations on both Bornholm and Zealand, as well as the Danish cable connection between the two.

The environmental assessment process has been extensive, with the documentation including an environmental report and several sub-reports—adding up to more than 4,300 pages. These documents detail the potential impacts and how they can be mitigated. Throughout the process, multiple public consultation rounds and information meetings on Bornholm and Zealand took place, inviting citizens, municipalities, and organizations to share questions, concerns, and local insights, which helped shape the final documentation.

As for next steps, although the environmental permit is now in place, major construction won’t start immediately. Preparatory activities—such as archaeological investigations, technical studies, landowner agreements, detailed planning, and tendering—still need to be completed, all in line with the permit’s requirements.

The full Bornholm Energy Island project, including the offshore wind farms, is expected to be commissioned in 2036. The cable between Bornholm and Germany (owned by 50Hertz) is undergoing a separate environmental process in both Denmark and Germany.

Picture: 50Hertz

At the North Sea Summit in Hamburg, Denmark and Germany reached an agreement on Bornholm Energy Island, including the allocation of costs related to offshore wind. German Chancellor Friedrich Merz and Danish Prime Minister Mette Frederiksen presented the funding framework negotiated between the two countries for the future offshore undertakings within the project. The agreement on the wind farms for the Bornholm Energy Island project marks the decisive building block for the realisation of this particular German-Danish infrastructure undertaking.

Thomas Egebo, CEO of Energinet: “The agreement is an important step in translating political ambitions into concrete projects and establishing clear frameworks for large-scale energy infrastructure projects. Energinet and 50Hertz have a long-standing cross-border cooperation. Together, we have, among other things, delivered the world’s first hybrid interconnector, Kriegers Flak, in the Baltic Sea. We will bring these experiences into the continued work on Bornholm Energy Island and the integration of offshore wind into the power system.”

Stefan Kapferer, CEO of 50Hertz: “The agreement between Germany and Denmark has an impact on the offshore industry across Europe, extending far beyond the Baltic Sea project Bornholm Energy Island. It is furthermore a strong european signal in geopolitically difficult times. Both countries are breaking new regulatory ground and are therefore pioneering the way forward. 50Hertz and Energinet will jointly contribute their expertise and experience and, as those responsible for the electricity hub on Bornholm and for the direct current connections to Denmark and Germany, will play their part in the success of the project overall.”

In the picture: German Chancellor Friedrich Merz and Denmark's Prime Minister Mette Frederiksen together with Denmark's Energy and Climate Protection Minister Lars Aargard, Energinet CEO Thomas Egebo, EU Energy Commissioner Dan Jørgensen, 50Hertz CEO Stefan Kapferer and State Secretary Frank Wetzel (f.l.t.r). Photo: Presse- und Informationsamt der Bundesregierung.

On Danish soil, the public consultation phase for the planned high-voltage cable connection between the Bornholm Energy Island and Germany has now begun. In Germany there have been public consultation formats earlier in 2025.

The consultation for the part located in Denmark – also known as the idea phase – is part of the environmental assessment process and is carried out by the Danish Agency for Green Land Use and Aquatic Environment (SGAV), which is the responsible environmental authority.

During this phase, citizens, organisations and authorities are invited to share knowledge, ideas and suggestions on which environmental and social aspects should be examined in the forthcoming environmental studies. 

The environmental assessment covers the part of the project located within Denmark – from the land cable connecting the converter station on Bornholm to the subsea cable up to the Danish–German maritime border.

As the consultation relates to this part of the project and follows Danish environmental procedures, the process – including an online public meeting on 26 November – will be conducted in Danish. For the Bornholm Energy Island (BEI) project, the information event is part of the mandatory public consultation process prior to submitting the permit application for a 'Project of Common Interest' (PCI).

The section of the project located in German waters  – from the maritime border to the landfall and converter station in Rappenhagen – will be subject to environmental assessment and permitting by the relevant German authorities.

Energinet and 50Hertz, the transmission system operators jointly developing the interconnector project, will support the consultation process by presenting technical information and answering questions during the online meeting.

The interconnector is part of the broader Bornholm Energy Island project, which will collect and transmit renewable power from future offshore wind farms in the Baltic Sea to both Denmark and Germany.

Further information about the consultation phase, the environmental assessment and the project – including details about the online public meeting – is available in Danish on Energinets website: www.energinet.dk/bornholminterconnector

The joint Danish-German Bornholm Energy Island project is moving from the planning and development stage to the implementation stage. The key components for the upcoming Bornholm Energy Island are now secured. Siemens Energy will deliver the high-voltage substations in both Denmark and Germany, while NKT will establish the cable connection between Bornholm and Zealand and as well between Bornholm and the German mainland.  

Minister for Climate, Energy and Utilities Lars Aagaard has given Energinet permission to take the next step in the project and invest in the electricity infrastructure for the upcoming Bornholm Energy Island.  

At the same time, Energinet and 50Hertz have signed a contract with Siemens Energy for advanced high-voltage equipment, which will constitute one of the largest individual tasks in the joint Danish-German project. The equipment includes four converter stations (HVDC) and one high-voltage station (HVAC), all of which will ensure that at least 3 GW of green power from offshore wind can be transmitted to both Danish and German consumers. Two of the converter stations and the HVAC station will be located near Aakirkeby on Bornholm, while the other stations will be built at Lindehøj on Zealand and the municipality of Kemnitz in the Vorpommern-Greifswald district in Germany.  

Energinet has signed a contract with NKT, which will handle both the production and installation of the advanced sea and land cables to connect Bornholm and Zealand and ensure that green power from offshore wind near Bornholm can reach consumers throughout Denmark. NKT has also entered into an agreement with 50Hertz, for the supply of cables for the connection between the Bornholm Energy Island and Germany as part of a larger framework agreement from 2023. 

The approval also means that the large support from the EU’s infrastructure program, Connecting Europe Facility (CEF), which was awarded earlier this year, can now be activated. The support amounts to 645 million euros – DKK 4.8 billion – giving the project a significant financial boost.  

The EU support was officially marked in connection with an informal meeting of energy ministers in Copenhagen on September 4. Attending were Climate Commissioner Dan Jørgensen, Christian Schmidt, Head of energy department at german ministry for economics and energy, Minister for Climate, Energy and Utilities Lars Aagaard, CEO of 50Hertz Stefan Kapferer, and Energinet's CEO Thomas Egebo.

In the picture (f.l.t.r): Thomas Egebo (Energinet), Stefan Kapferer (50Hertz), Dan Jørgensen (Commissioner for Energy and Housing), Lars Aagaard (Danish minister for climate and energy), Christian Schmidt (Head of energy department at german ministry for economics and energy).

Co-financed by the Connecting Europe Facility of the European Union

The European Commission has provided funding from the Connecting Europe Facility (CEF) program in the amount of 645 million EUR - underlining the importance of green transition for The European Union and providing financial support for the world’s first hybrid direct current interconnector

The project, which is jointly developed by grid operators 50Hertz and Energinet, includes a power hub on the island of Bornholm with two converters, direct current connections to the Danish and German mainland and additional converter systems there for converting direct current into alternating current. This infrastructure will be used to harvest the planned three gigawatts of power from offshore wind farms of Bornholm and make it available to the electricity markets in Germany and Denmark in line with demand.  To this end, it is the first time Energinet and 50Hertz have issued a joint tender of cross border electrical infrastructure.

Bornholm Energy Island is an innovative project that can serve as a model for further interconnections in the North and Baltic Seas. Before the start of the next project phase, which includes the signing of contracts for converters, transformers and other substation technology, regulatory clarity is needed on the German and Danish side. Consequently, the TSOs are not able to sign contracts in their current tender The signing of the contracts has therefore been postponed.  Consequently, the signing of contracts in the ongoing tender will not yet be done.

Energinet and 50Hertz will continue their close cooperation in dialogue with the Danish and German governments.

Since May 2023, Bornholms Museum has conducted archaeological pre-investigations of an area of almost 120 hectares near Aakirkeby, where the land facility for Bornholm Energy Island will be built.
Bornholms Museum has pointed out an area of more than 35 hectares for excavations. The excavations will become the largest ever on Bornholm. First step is an area of 8 hectares in the southern part, where four settlements have been discovered. Here 6 archaeologists will dig a bit deeper to discover and investigate more traces from the past.
The pre-investigations have already given a unique overview of the cultural landscape in the area up to 6,000 years back. They have shown traces back to the New Stone Age, when agriculture came with the first farmers across the Baltic Sea, the Bronze and Iron Ages and Viking Age.
Among the finds are flint tools, pottery shards, a stone with rock carvings, more than 100 houses, settlements, and a few graves. Some of the finds are unique and tell the story of Bornholm's special role in trade, culture, and religion in the Baltic Sea area.

Photos: Bornholm's Museum has pointed out an area of approximately 35 hectares for excavation (marked with red) in the location of the land facility for Bornholm Energy Island.

11.10.2024 – Stations that blend with the landscape and a design that adds recreational value to the area are some of the focal points of the local plan for the onshore stations to Bornholm Energy Island.

The Bornholm Regional Municipality have formally adopted the local plan for the area of the onshore station to Bornholm Energy Island near Aakirkeby – the main town in the southern part of Bornholm. The plan emphasizes the integration of the stations into the landscape, minimizing environmental impact and adding recreational value to the area.

Prior to the local plan the ​Regional Municipality of Bornholm carried out several public consultations regarding the municipality plan supplement and the local plan in the period of 2022 to 2023.

An architectural process involving the local community has been a further but important step due to the impact of the large and significant construction on Bornholm. The local community were invited by Energinet and the municipality to participate in the process – drawing on their experiences and wishes. Two workshops were held in November 2022 and March 2023, where ideas and concepts were tested.

About Local plan no. 152 for Bornholm Energy Island onshore stations

The local plan sets out the framework for guiding planning decisions in the designated area of the BEI onshore stations including the converter stations, DC breakers, AC substations and connection to the wind turbines.

Next step will be the second public hearing on the environmental impact assessment for the Danish part for the process later this year.

About Municipality plan supplement no. 20 for area use for the BEI onshore stations

The municipality plan supplement regulates the use of areas in a municipality. In this case an area for the onshore stations near Aakirkeby – the main town in the southern part of Bornholm. This plan also sets the framework for the local plan.

An environmental report that summarizes the potential impact of the local plan has been produced alongside the local plan and the municipality plan supplement.

07.05.2024 – No energy transition without energy transmission – this was the title of one of the panel discussions at the annual event Baltic Energy Island Summit 2024.

CEO Stephan Kapferer from 50Hertz and Vice President Hanne Storm Edlefsen from Energinet discussed the challenges we need to tackle to derisk and increase efficiency when going from small energy system elements to large scale. A key topic was the energy islands – how and why they are necessary in EU to reach 2030 and 2050 targets. State Secretary for Energy, Federal Ministry of Economic Affairs and Climate Action, Phillipp Nimmermann joined the discussion bringing up perspectives on the importance of cooperation.

More about the annual international event Baltic Energy Island Summit

On May 6th and 7th 2024 politicians, professionals, researchers and others working in the field of energy transition worldwide meet on the Danish Island Bornholm to discuss the future of sustainable energy systems, the societies which they power and transform, and the opportunities they provide.

30.11.2023 – Danish and German TSO’s Energinet and 50Hertz have started the tendering process for key technologies of the joint project Bornholm Energy Island that will bring 3 GW of green power to German and Danish energy consumers. As a result of a market dialogue with possible vendors this summer, the partners decided to speed up the tendering in order to reserve production capacity as early as possible. Next step will be receiving bids and starting negotiations until contracts can be signed in the second half of 2024.

The market dialogue with interested vendors have shown that the Energy Island project needs start tendering early in order to reserve production capacity and keep to the project timeline. Another direct consequence of the market dialogue is that 50Hertz and Energinet will split the tender into multiple contracts in order to enable vendors interested in bidding on the HVDC stations and cables the possibility to bid on contracts within their core business, while other parts of the project will be tendered separately.

HDVC equipment for the stations in Germany and Denmark will be tendered as one joint contract which has been sent to prequalified vendors today. 50Hertz and Energinet has designed the procurement of the HVDC-breakers – a future key technology for the energy island - as an option, which can either be built as part of the initial construction – or as a separate tender at a later phase. The reason for this is that some vendors are highly interested in supplying the breakers, while others prefer to focus on their core products.

”We cannot ignore the current market situation. HVDC circuit breakers will play an important part in the operation of our Energy Island but are not crucial in the initial phase. Therefore, we have decided that it is more important to ensure a competitive bidding process and to keep up the pace of the green transition in order to secure the supply of clean electricity to consumers in Germany and Denmark.”, says Hanne Storm Edlefsen, vice president for Energy Islands at Energinet.

50Hertz has already signed a contract for the procurement of HVDC cables for Bornholm Energy Island and several other projects. Energinet has started the tender of one contract for production of cables as well as offshore installation. Onshore installation and horizontal directional drillings (HDD) will be a separate contract as well as surveying and removal of unexploded ordnance (UXO) which will also be tendered as a separate contract at a later time. Civil works and the buildings for the HDVC stations will be tendered for Denmark and Germany respectively, at a later time.

Construction on Energinets part of the project in Denmark can start once it has received an environmental permit and archaeological excavations have been completed in 2025.  In Germany installation and construction can start after permits are granted by the authorities.

50Hertz just signed a contract regarding the manufacturing and installation of 3,500 kilometers of 525 kV HVDC cables. This includes on- and offshore cables for the German connection of Bornholm Energy Island. The cable system will have a total length of 164 kilometers, with the vast majority of 149 kilometers being offshore cables. Danish company NKT was awarded with this contract. 

The BEI connection will consist of two cable cores and an additional metallic return, making 492 kilometers of cables in total. Our subsea cables will meet the shoreline, and connect to our existing grid, in the Lubmin county. 

50Hertz’ planned connection will allow a transmission capacity of 2,000 MW and is a vital part of our joint project with Energinet.  

At the 12th Future Wind & Maritime Conference in Rostock (Germany), the new 50Hertz programme director for the Bornholm Energy Island (BEI) project, Dettmar Knieriem, presented the main features and advantages of this joint German-Danish project to an interested audience of experts. BEI will act as a hub for 3 GW of offshore wind energy in the future. On the Baltic Sea Island, the electricity will be converted from AC and DC voltage and then transmitted via powerful 525 kV sea and land cables both to Germany and to the Danish mainland.

Knieriem explained that the tender process for key components had already started and that a market dialogue had also taken place in early June with potential suppliers and service providers for cables and converter facilities. The tendering process started in the first quarter of 2023, with the awards taking place one year later. The schedule envisages that the construction of the converter plants in Germany and Denmark could possibly begin in 2026.

Another boost for Bornholm Energy Island: Robert Habeck, Federal Minister for Economic Affairs and Climate Action, and his Danish counterpart Lars Aagaard confirmed their signing of the agreement during the European energy ministers meeting in Luxembourg on Monday, 19^th of June. The agreement between the Danish and German governments creates the conditions to realize the innovative power hub on Bornholm and several hundred kilometers of 525 kV direct current sea and land cables.

Stefan Kapferer, CEO of 50Hertz: "Bornholm Energy Island paves the way for a future in which offshore wind energy will no longer be accessed exclusively by individual countries via point-to-point connections. In the future, part of the offshore electricity produced flow to wherever the greatest demand is via offshore DC grids. The Bornholm Energy Island project will also be used for electricity to be traded between Germany and Denmark. This is economically viable and will increase both countries’ security of supply under new geopolitical circumstances.”

Thomas Egebo, CEO of Energinet: “For Denmark and Energinet, the deployment of very large-scale offshore wind farms and interconnectors is also an important part of politically mandated ambitions and wider plans to export both green electrons and green molecules via a future hydrogen backbone in Denmark. That is supporting the decarbonisation of Germany’s industrial sector. This joint project in the Baltic Sea and our projects in the North Sea will have an enormous impact on Europe’s energy transition.”

With Bornholm Energy Island Energinet and 50Hertz are not only doing pioneering work from a technical point of view. Negotiations between the two companies and their respective governments have also clarified ownership rights and the allocation of target renewable energy quantities. Under the agreement, both grid operators will equally bear the infrastructure costs for the project and also equally share the renewable energy target amounts. 50Hertz and Energinet will also split the congestion revenues linked to the power lines that will lead to Germany and Denmark equally.

Premiere at Wind Europe Conference: The joint project of Energinet and 50Hertz presented itself publicly for the first time at the major event of the European wind industry on a large stage. At the joint stand of Elia Group and Energinet, the focus was on the topic of energy islands - including, of course, Bornholm Energy Island.  In short info sessions various project representatives gave an insight into the planning of the electricity hub on the island of Bornholm, which lead to interesting discussions with many visitors

Moritz Wienhold, project manager at 50Hertz: “Presenting the Bornholm Energy Island project at the Wind Europe conference offered a great opportunity to get new insights and perspectives from stakeholders all over the industry”.

Casper Bruselius Jessen, deputy project director Energinet: “Leaving Wind Europe in Copenhagen with many fruitful and constructive discussions, we are now looking forward to continue the work on our joint project.”

The Market Dialogue for Bornholm Energy Island just started. You can find the information right here on the Bornholm Energy Island website.